Time Travel Paradoxes and Entangled Timelines

Abstract

For time travel to be consistent with the known laws of physics, the resulting paradoxes must be resolved. It has been suggested that parallel timelines (a.k.a. multiple histories) may provide a resolution. However, so far, a concrete mechanism by which parallel timelines can be created has never been satisfactorily formulated. In this paper we propose such a mechanism within the framework of unmodified quantum mechanics, also known as the Everett or "many-worlds" interpretation. The timelines in our model are emergent, like the "worlds" of the Everett interpretation; they are created by quantum entanglement between the time machine and the environment. Therefore, we call them "entangled timelines" or E-CTCs. As the entanglement gradually spreads out to additional systems, the timelines spread out as well, providing a local and well-defined alternative to the naive "branching timelines" picture often presented in the literature. The E-CTC model is similar to Deutsch's familiar D-CTC model, but differs from it mainly by making the entanglement explicit, which allows us to create a clearer practical definition of the resulting parallel timelines.